The genetic structure of alcohol sensitivity(AS) by interview, alcohol dehydrogenase(ADH) and aldehyde dehydrogenase(ALDH) in Korean population were studied. Two hundred liver samples obtained from the induced abortuses aging 6 to 7 months of gestational age and hair root cells from 300 healthy adults were analyzed for the gene frequency of ADH and ALDH by electrophoresis. The results obtained from the interview and electrophoresis were revealed that 77% of Korean were known to be alcohol sensitive after alcohol administration and 87% of Korean were carried an atypical liver ADH. The enzyme activity of atypical liver ADH was much higher than that of usual liver ADH. In the case of ALDH two forms of ALDH, ALDH-1 and ALDH-2, were demonstrable by electrophoresis in both liver and hair root cell samples, however, the ALDH-1 activity was very weak in hair root cells. The frequency of ALDH-1 deficiency in liver and hair root samples were 36% and 34%, respectively. However, no variants were observed in ALDH-2. The frequencies of alcohol sensitivity, atypical liver ADH and ALDH-1 deficiency in Korean population were very high comparing the frequencies in Caucasians but no big differences among the orientals.